Conspecific nest parasitism in the European starling (original) (raw)
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Egg removal and intraspecific brood parasitism in the European starling ( Sturnus vulgaris )
Behavioral Ecology and Sociobiology, 1989
Jersey for evidence of intraspecific brood parasitism and egg removal during the laying period. Egg removal occurred significantly more often at nests where intraspecific brood parasitism was detected (12 of 35 nests, 34%) than at unparasitized nests (23 of 249 nests, 9%). Brood parasitism (92% of parasitized nests) and egg removal (74% of nests with egg removal) were most common at nests where egg laying began in April of each year (i.e., early nests). Egg removal occurred at 26 (19%) and brood parasitism at 32 (23%) of 138 early nests. Both brood parasitism and egg removal were concentrated during the first four days in the laying period when brood parasitism is most likely to be successful and when host nests are most vulnerable to parasitism (Romagnano 1987). Both parasitism and removal usually involved a single egg at each nest. We detected brood parasitism and egg removal on the same day at five of 12 nests (42%) where both were observed. Because starlings do not remove foreign eggs from their nests once they begin laying we hypothesize that parasite females sometimes removed host eggs while parasitizing nests.
The Parasitism Insurance Hypothesis: Why Starlings Leave Space for Parasitic Eggs
The Condor, 1989
We propose that European Starlings (Sturnus vulgaris) leave space for intraspecific parasitic eggs in order to prevent parasitism from producing an overcrowded clutch. For this hypothesis to be applicable, a species must have altricial young, determinate laying, and a high frequency of intraspecific brood parasitism. The hypothesis predicts that (1) host clutches will be smaller than would be predicted were only productivity considered, (2) brood parasitism will only moderately depress host reproductive success (RS), and (3) the actual frequency of net brood parasitism will exceed the threshold frequency (where the alternative tactics of leaving space and not leaving space produce equal results). Two models are presented for locating the threshold frequency: the either-or model and the graded model. The hypothesis was tested on early clutches of starlings in New Jersey, using a combination of nest censusing, weighing, electrophoretic analysis, and analysis of postovulatory follicles. The results were consistent with all predictions. (1) Clutch size five (c/5) was the most common but c/6 was the most productive while c/7 was overcrowded. (2) Parasitism had only a slight dampening effect on host RS. (3) At least 33.3% of clutches suffered net brood parasitism: 2 1.2% suffered the net addition of one egg while 12.1% suffered the net addition of two or more. These rates are above the threshold frequencies generated by both models. Five alternative explanations for our results were explored but none fit the data as well as the parasitism insurance hypothesis.
Coproparasitological study of European starling nestlings (Sturnus vulgaris) in Argentina
TURKISH JOURNAL OF ZOOLOGY, 2016
Invasive species are particularly susceptible to certain natural enemies, such as the parasites they encounter in the introduced range. However, if invaders become resistant to these parasitic infections, they improve the likelihood of increasing their population (Blackburn et al., 2009). On the other hand, parasites may be lost during or soon after the introduction process (Torchin et al., 2003). This release from the effects of natural enemies may contribute to the rapid establishment and proliferation of nonindigenous species (Torchin and Mitchell, 2004). The European starling Sturnus vulgaris (hereafter starling) is a bird native to Europe, Asia, and North Africa. It has been successfully established in New Zealand, Australia, South Africa,
Journal of Avian Biology, 2015
Nest-dwelling ectoparasites represent an early stressor for birds as they impair the development of nestlings, which can adaptively respond by adjusting their growth rate to current conditions. While nest ectoparasites have long-term eff ects on nesting adults, no study has examined if they also have an impact on the moult patterns of juveniles. Herein, we investigated whether the presence of ectoparasites in the nest infl uences the start and duration of the fi rst pre-basic moult in the European starling. To do so, we experimentally removed nest-dwelling ectoparasites from a group of nests and used another group of unmanipulated (i.e. naturally infested) nests as the control. Th e moult began at an earlier age and lasted longer in birds from the ectoparasite-free nests compared to their control counterparts. Th e timing of the moult was also aff ected by the hatching date (i.e. birds that fl edged later had shorter moults) and the brood size (i.e. birds in larger broods started their moult at an older age). We also found evidence that the removal of nest ectoparasites infl uenced the condition of individuals during the course of the moult. In the control birds, we observed a decrease in hematocrit levels, but these were unaltered in the birds fl edged from the ectoparasite-free nests. Our study shows that nest-dwelling ectoparasites adversely aff ected the timing of the moult and the individual condition of juvenile starlings, with possible major consequences for their subsequent life-history events.
Brood parasitic European starlings do not lay high-quality eggs
Behavioral Ecology, 2005
Chicks of obligate brood parasites employ a variety of morphological and behavioral strategies to outcompete nest mates. Elevated competitiveness is favored by natural selection because parasitic chicks are not related to their host parents or nest mates. When chicks of conspecific brood parasites (CBPs) are unrelated to their hosts, they and their parents would also benefit from traits that enhance competitiveness. However, these traits must be inducible tactics in CBPs, since conspecific brood parasitism (CBP) is facultative. Such tactics could be induced by resources passed to offspring through the egg. Thus, females engaging in CBP should allocate to their eggs resources that will enhance offspring competitiveness. We tested this prediction in a population of European starlings (Sturnus vulgaris) breeding in southern Sweden. Previous research showed that almost all CBPs in this population are floater females that have yet to breed in the current season. We identified putative brood parasitic eggs through monitoring egg laying and verified parasitism using protein fingerprinting. We then determined whether parasitic eggs were larger, larger-yolked, or had higher concentrations of yolk testosterone or androstenedione than control eggs. The 14 brood parasitic eggs laid in active nests (those with clutches of at least two eggs that were eventually incubated) did not differ from controls in any of these characteristics. Ten dumped eggs, laid in nonactive nest-boxes or on the ground, were smaller and smaller-yolked than control eggs but did not differ in yolk androgen concentrations. The failure of our prediction could be the result of high costs of investing in eggs, lack of competition-based benefits for chicks, or physiological constraints on egg manipulation.
Immunocompetence and Parasitism in Nestlings from Wild Populations
The Open Ornithology Journal, 2010
Nestling is a defenceless stage in the life of birds in several ways. For instance, the possibilities to escape infection and infestation by several parasitic diseases are greatly reduced in nestlings. This fact implies that a number of strategies and counter strategies could evolve in hosts to avoid parasites and in parasites to locate and exploit young hosts. An increasing number of nestlings in a nest may support more parasites and thus increase competition between siblings to avoid parasitism. In addition, parental effort may vary in the presence of parasites resulting in different effects of parasitism on nestlings. Moreover, nestling investment in immunity may increase in the presence of parasites at least up to a limit marked by the ability of parents to get resources for their nestlings. In this respect, the transfer of immunoglobulins and other resources from the female parent to eggs may be of considerable importance during the first days of nestlings´ life. However, increased parental activity may also attract more parasites to the nest. A recent work using a metaanalytical approach suggests that parasite-induced nestling mortality in birds is mainly determined by geographical location and to a smaller extent nest site and parasite prevalence. The naïve immune system of nestlings and the difficulties to avoid infection once the nest has been located, imply a high potential impact of parasites on nestlings. Thus parasites could cause an important reduction of host population productivity through their effects on nestlings.
Ethology, 2012
The prospective behaviour for nests by conspecific intruders may be a strategy to gather public information for future reproduction or to secure resources for immediate reproduction. Although the relationship between the sex, age and breeding experience of intruders and the sex and age of residents may be crucial for understanding the significance of nest-prospecting behaviour, a precise determination of these traits has rarely been addressed in field studies. In a free-ranging population of spotless starlings (Sturnus unicolor), inexperienced birds were the predominant intruders. The ratio of male-to-female intruders was higher among birds without previous breeding experience, although our results did not allow us to determine whether more inexperienced males or females intruded nests. The average annual rate of intrusion of either sex was strongly correlated with the number of fledglings produced in the study colony the previous year, which seems to indicate that the inexperienced intruders were, in general, yearlings. The proportion of the sexes among the intruders in each study year was correlated with the average age of male owners but not with the age of female owners. This result suggests that the presence of intruding males in the nests was affected by an increased opportunity to find vacancies in nesting territories as resident males became older. This finding supports the hypothesis that, in most cases, birds visited nests to obtain personal information about nesting resources. However, the intrusion rates were higher when there were nestlings than during the incubation period, which suggests that collecting public information was also involved in the intruding behaviour. Both sexes regularly attacked intruders, which implies that the intruders inflicted some kind of cost on the owners. Female floaters were more frequently chased, probably because they regularly lay parasitically in conspecific nests.